Production of organic acids and salts thereof from cellulosic materials



2,750,414 PRODUCTION OF ORGANIC ACIDS AND SALTS THEREOF FROM CELLULOSICMATERIALS Kenneth G. Chesley, Crossett, Ark., Charles W. Montgomery,Baton Rouge, La., and Lloyd T. Sandborn,

Crossett, Ark, assignors to Crossett Lumber Company,

Crossett, Arln, a corporation of Arkansas No Drawing. ApplicationNovember 3, 1952, Serial No. 318,533 17 Claims. (Cl. 260528) Thisinvention relates to the production of organic acids and salts thereof,and more particularly to a process of producing said materials wherein amixture of cellulosic material and an aqueous alkaline solution isheated in a closed system.

It is well known that a number of organic acids can be produced byheating various cellulosic materials with alkali and alkaline solutions.For example, it is known that sodium acetate and sodium formate areformed in the soda and sulphate wood pulping processes; that oxalic acidcan be made by the alkaline fusion of cellulosic materials; and thatlactic acid can be produced by the action of caustic soda on simplesugars. In our copending applications Serial Numbers 318,531 and 318,532filed November 3, 1952 we disclose that black liquor from the sulphatewood pulping process contains substantial quantities of sodium lactateand sodium glycolate in addition to the previously known sodium salts ofacetate and formate.

As set forth in the present invention we have further discovered thatthe salts of acetic, formic, lactic and glycolic acids can be producedfrom a variety of cellulosic materials, simultaneously and in improvedyields over these obtained in said wood pulping process. Furthermore, wehave discovered a process for producing these acids and salts thereof inwhich the formation of undesirable organic materials is substantiallyreduced.

An object of the present invention is to provide a process for producingorganic acids and their salts; A further object is to provide such aprocess characterized by high yields, simplicity and economy; Otherobjects will be apparent from the description of this invention givenhereinafter.

The above and other objects are accomplished according to this inventionby carrying out the herein described process of producing saturatedmonocarboxylic acids having 1-3 carbon atoms in which one of thehydrogen atoms on the carbon atom adjacent the carboxyl group may besubstituted by an hydroxyl group, which comprises subjecting a mixtureof cellulosic material and an aqueous alkaline solution to a temperatureof 250 C.-300 C. in a closed system, acidifying the reaction mixture andthereby obtaining a mixture of said acids in aqueous solution. Among theacids which form, formic, acetic, lactic and glycolic are of primaryinterest according to this invention. If the salts of the said acids aredesired, the above acidification step is omitted. Although thisinvention is applicable to the production of organic acid salts, for thesake of simplicity and clarity it will be describedfor the most partwith reference to the production of organic acids.

Cellulosic or so-called ligno-cellulosic materials in general areapplicable to this invention, typical examples of which include wood,bark, straw, bagasse, sericea, pure cellulose, and the like, It is knownthat formic, acetic and lactic acids can be produced from simple sugars,such as glucose, by treatment with alkali at temperatures obtainableunder atmospheric pressure. It is considered. that the cellulose andhemicelluloses in cellulosic materials probably break down into simplercarbohydrates which are. capable of yielding organic acids under thehydronited States l atent' C) "ice lytic conditions of this invention.It is known that oxalic acid is the major product obtained by heating asubstantially dry mixture of cellulosic material and alkali in thepresence of oxygen. The formation of oxalic acid does not occur to anysubstantial extent during the process of this invention.

Lignin in the cellulosic material does not contribute significantly tothe yield of the desired organic acids, but it is known that lignin willreact with sodium hydroxide to give phenols and a variety of othermaterials which may be by-products in the present invention.

We have found that substantially pure cellulose under the process ofthis invention will yield the four desired acids, however it is muchless preferred than the other raw materials disclosed herein. It appearsthat the hemicellulose content of the cellulosic material is animportant contributing factor to the yield of acids obtained during theprocess of this invention. Therefore, in addition to economic reasons,we prefer to use a starting material such as wood, bark, straw, etc.Thus the term cellulosic material is used herein to cover, in additionto cellulose per se, materials which contain other carbohydrates of thetype commonly classified as hemicellulose.

The process of our invention requires that the cellulosic materials bereacted with alkali and water in the liquid phase, therefore the alkalirequired may be broadly defined as an aqueous alkaline solution. It ispreferred to use an alkali selected from the group consisting of watersoluble hydroxides and carbonates of alkali metals and alkaline earthmetals. The sodium compounds are preferred for reasons of economy,however, potassium and lithium compounds are approximately equal intheir reactions to the sodium compounds. Barium hydroxide is a suitablealkali but its cost renders it less attractive. Calcium hydroxide isless desirable than the sodium compounds because of its lower Watersolubility.

The above definition of suitable alkalies is also intended to includeimpure alkaline solutions such as the spent liquor from alkaline woodpulping processes commonly known as black liquor, partially spent liquorfrom the process of this invention which may be refortified or used asis in succeeding cooks, and other similar impure solutions containingsuitable alkali.

Preferably either sodium hydroxide or sodium carbonate solutions will beused, and which one of these is used will depend on the specific resultsdesired. Sodium hydroxide is less selective than sodium carbonate asregards the constituents of cellulosic materials with which it willreact. It is known that even below 200 C. sodium hydroxide is capable ofreacting with lignin to render it soluble in aqueous alkaline solution.We have found that under the conditions of our invention practically allof the wood becomes soluble in sodium hydroxide. Several of ourexperiments show this, e. g. in several instances in which a mixture ofoak sawdust and sodium hydroxide was heated at 260 C., the insolubleresidue remaining at the end of the cook amounted to only 6%- 9% of theinitial weight of the wood. if in addition to the organic acids onedesired to obtain phenolic materials (e. g. catechol) from lignin,sodium hydroxide or other alkali metal hydroxide may be used.

It has been found according to this invention that sodium. carbonatepossesses certain advantages over is an efficient source of alkali forthis invention.

3 Sodium carbonate gives acids of a higher purity. For example, when amixture of wood and sodium carbonate is cooked at 260 C. for one hour,the amount of insoluble residue that remains is about 26%35% of the woodinitially used as compared with only about 6%-9% when sodium hydroxideis used. Thus when sodium hydroxide is used a larger amount of theundesired materials is associated with the sodium salts of the desiredorganic acids in solution. Acidifying the solution to liberate the acidsfrom their salts and removing the undesirable residue leaves a mixtureof the desired acids in aqueous solution regardless of which alkali isused, but it is more diificult to purify these acids when sodiumhydroxide is used. They may be purified by conventional solventextraction or they may be purified and separated by one of the processesdisclosed in our copending applications referred to hereinbefore. Thefact that this large amount of residue remains indicates that sodiumcarbonate is relatively inert toward those components of the wood whichare not involved in producing the desired acids. Consequently less ofthe sodium carbonate is used up in side reactions than is the case withsodium hydroxide, thereby leaving more of the sodium carbonate availablefor producing the desired acids.

Another advantage of using sodium carbonate as compared with sodiumhydroxide relates to the ease of recovery and reuse of excess alkali.This is especially true if the acids are purified by employing theprocess dis- 1 closed in the first of our above mentioned two copendingapplications.

The process of said copending application involves treating concentratedalkaline liquors of the sodium salts of the desired organic acids withalcohols to precipitate certain impurities and leave the sodium salts ofsaid acids in a more nearly pure state in the alcohol solution. Anysodium carbonate that remains in solution is precipitated from thealcohol and therefore is not present to consume mineral acid when it isused to liberate the organic acids from their salts. Since sodiumcarbonate is much less soluble in alcohol than is sodium hydroxide, itcan be removed more completely and thus permit an important economy. Theorganic matter precipitated by the addition of alcohol and that which isin the form of a precipitate at the end of the cook, contains somesodium. When this organic matter is burned, e. g. in a pulp millrecovery furnace, to recover its heat value, the soda is recovered assodium carbonate which can be re-used directly in the process of thisinvention.

Another favorable source of alkali is the black liquor that results fromalkaline pulping processes such as the soda or sulfate process. Blackliquor contains, in addition to the organic materials which havedissolved in the liquor during pulping, appreciable amounts ofsodiumhydroxide and sodium carbonate. Black liquor from the sulfateprocess also contains some sodium sulfide which As pointed outhereinbefore, black liquor already contains I appreciable amounts of thedesired organic acids.

As would be expected, the use of black liquor as a source of alkali isadvantageous to the extent of its content of alkali and the desiredorganic acids. We have found that black liquor also contributesadvantages in addition to those normally expected. The amounts of lacticand glycolic acids formed during cooking are larger than would beexpected from treatments under similar conditions with equivalentamounts of sodium hydroxide and sodium carbonate. A further advantage inusing black liquor as a source of alkali is that during the cook .thereis a very favorable precipitation of undesirable organic matter from theblack liquor so that the solids obtained at the end of the cook may begreater than the Weight of the wood at the start. This precipitate iseasily removed by simple filtration.

The reaction of our invention is carried out at a ternperature of 250C.-300 C. The temperature employed is critical. Below 250' C. the yieldsare undesirably low. Above 300 C. a substantial part of the acidsproduced, except acetic, is destroyed. Among other things, Example 4hereinafter shows the role of temperature. A temperature of 260 C.280 C.has been found to produce the best results.

Within quite broad limits reaction time is not a critical factor,however a period of about one hour has been found to be mostsatisfactory under most conditions. A substantial amount of acids isobtained after cooking only 15 minutes at 260 C. Cooking in excess of anhour produces no marked increase .in yield.

The Examples hereinafter give a number of illustrations of the effectthe amount of alkali used has on yield of acids. The manner in which theyield of acids varies with the amount of alkali used depends on Whatbasis is used to determine yields. In general the following conclusionsare true. If acid yields are based on wood used, they vary directly withthe amount of alkali used. If acid yields are based on alkali used, theyvary inversely with the amount of alkali used. The data in Table 8-A ofExample 8 hereinafter support these conclusions. Technically it does notmatter whether an excess of alkali is used, but economically the amountof alkali used will depend on the relative cost of wood and alkali.Ratios of wood to alkali will be chosen that will give the lowestpossible cost of production. If waste wood is used, acid yields based onalkali will be of greater significance than the yields based on wood,and desirably one will use lower amounts of alkali rather than aimingfor the maximum possible yields based on wood.

When black liquor is used, within obvious limitations dependent on therelative amounts of black liquor and waste wood available, it is moreeconomical to operate at higher ratios of alkali to wood. To a certainextent black liquor is a cheap source of alkali, provided a large partof its soda is eventually returned to the pulp mill recovery system in aform suitable for preparing fresh pulping liquor. Since a large part ofthe soda will be returned as sodium sulfate, this will determine theamount of black liquor which may feasibly be used for the purposes ofthis invention. The reason for this is that although addition of acertain amount of sodium sulfate to the pumping process is desirable,there is a limit beyond which it is impractical to go.

It is important that water be present in the liquid phase during thecooking or heating period. Therefore cooking must be carried out in aclosed system and of course under the autogenously developed pressure atthe temperature employed. Although the presence of liquid Water isessential, the amount is not critical. We have obtained best resultswith about 7 to 8 volumes of aqueous solution to one part by weight ofwood. Smaller volumes are satisfactory but give somewhat lower yields ofacids. Larger volumes may be used but it is economically undesirablebecause of the needless expense in providing larger equipment forhandling the excess water.

When operating with the preferred volumes, the concentration of thedesired acids in the cooking liquor is about 30-35 grams per liter whenwood is being treated with sodium hydroxide or sodium carbonate. We havefound that this concentration can be increased to at least 100 grams perliter by re-use of the cooking liquor from one cook as makeup solutionfor the next cook. Example 6 hereinafter illustrates this. If blackliquor is used as alkali, the extentto which the cooking liquor can bereused. to build up the concentration of acids depends on theconcentration of black liquor used. Usually one would obtain the blackliquor at a point in the pulp mill recovery system just after the talloil soap has removed, and this black liquor contains about 300-325 gramsof solids per liter. At this concentration no further dilution isnecessary, and after a single cook it contains about grams per liter ofthe desired acids. When starting with this concentration of blackliquor, normally 5. it is not as desirable to increase the concentrationof the desired acids by re-use of the cooking liquor as it is when usingother alkalies, as described above, because the concentration of acidsis already quite high and because it is diificult to maintain thedesired ratio of water to wood. However, if more concentrated blackliquor is initially used, the concentration of acids can be furtherincreased by re-use of cooking. liquor without. interfering with usingthe preferred waterto wood ratio.

The following examples illustrate specific embodiments of thisinvention, but the invention is not limited thereto except as defined inthe appended claims. In the examples, per cent is by weight.

Four difierent apparatus were used in carrying out the experimentsdisclosed in the examples. The apparatus used is specified in eachexample. One type apparatus was a one liter, stainless steel,electrically heated auto- EXAMPLE 1.

The data in Table 1 below show the yields of acids obtained by cookingoak sawdust with sodium hydroxide at 260 C. The wood was-mixed with theaqueous solution of sodium hydroxide and the mixture placed in apressure vessel and heated; Runs 1, 2 and 3 were made in an electricallyheated steel bomb with agitation. Runs 4 and 5 were made in a threegallon gas fired autoclave without. agitation. At the end of thepressure cook, the amount of. insoluble solid. amounted to only 6%9% ofthe starting weight of the wood. After heating, the pressure vessel wascooled to a temperature below 100 0., opened and the contents filteredto remove the small amount of insoluble material present. A portion ofthe filtrate was then acidified with sulfuric acid to liberate the freeorganic acids and theiacidic solution was analyzed for the four desiredacids.

Table 1 GME l Percent eld based on W d Run Wood, NaOH, NBOH Vol., Y1 o0per 100 260 No. grams grams grams ml. 0 hrs wood Acetic Formic LacticGlycolic 50 Z 14. s 0. 74 250V 2 4. e 7. 0 13. 2 50 80 4. 0 400 2 9. 47. 0 8.8 8. 2 50 9. 3 47 350 2 4. 2 4. 1 8. 2 9. 4 400 118. 4 74 3,000 14. 1 8. 4 8. 2 6. 1 400 150 94 000 1 3. 8 8. 8 8. 7 7. 9

GME is gram molecular equivalent. Amount: of glycollc acid was notdetermined.

clave equipped with a stirrer. Another apparatus used EXAMPLE 2 was thesame as that just described except its size was five gallons. Anothertype was a three gallon, steel, gas fired autoclave with no stirrer.Still another type of apparatus comprised three separate containers eachmade of one 1800 milliliter iron tube and immersed in water in a threegallon steel autoclave with no stirrer. With the latter type apparatusit was possible to simultaneously Table 2 lab/$153) R 1d Percentgelddbased on 2 3 as He 00 Run No. grams grams per 100 Tune percent WoodN 32003 grams m1. Hrs. of Wood wood Acetic Formic Lac. Gly.

50 0.47 350 2 I 4.5 7.2 9.9 9. 50 100 1.9 350 2 8.4 as 8317- 50 37. 5 0.71 350 2 3. 5 6. 7 9. 6 9. 2 400 200 0. 47 3, 785 1 24 3. 8 7. 8 9. 9 9.2 400 160 0.38 3,000 1 I 32 i 4.2 6.7 5.9 5.1 400 120 0. 28 ,000 1 35 4.1 6. 5 5. 4 4. 9 400 160 0. 38 3,000 2 30 4. 0 7. 5 7. 1 5. 0 400 160 0.38' 3, 000 $4 48 3. 6 5. 4 4. 4 3. 4 400 200 0. 74 3, 785 2 22 4. 5 8. 47. 8 6. 3 400 200 o. 74 3, 000 1 4. 2 7. 4 6. 2 6. 0

1 Value not determined.

make three cooks and to make them under more nearly EXAMPLE 3 identicalconditions than with separate cook-s. The type apparatus used is givenmerely for completeness of disclosure and not in an attempt to show thatthe invention is limited thereby or by any other particular apparatus.While the type of apparatus which one uses may have some bearing on theresults one obtains, from the results we have obtained one would not bejustified in recommending a particular type of apparatus asbeingsubst-antially better than another. In any event, the selection ofany one of a number of specific types of useful apparatus for practicingthis invention is well within the purview of those skilled in the art.

In the examples and elsewhere herein, the amounts of formic, acetic,lactic and glycolic acids were determined by the partitionchromatographic method described by Marvel and Rands in the Journal ofthe American Chemical Society, 72, 2642 (1950).

In a series of runs, hardwood sawdust was cooked with various amounts ofblack liquor from a sulfate pulping process. The black liquor was takenfrom the pulp mill recovery system after it had been concentratedsufiiciently to permit removal of tall oil soap. The liquor contained400 grams of solids per liter. By titration of a diluted sample of blackliquor with standard acid, it was found that 10.4 ml. of 0.5169 N HClwas. required to bring, the pH. of 5 ml. of the black liquor to pH 8.3.From this value, it was calculated that each liter of black liquorcontained an amount of available alkali equal to 1.075 molecularequivalents of NaOH. The organic acids content of the black liquor wasfound to be 8.7, 16.3, 11.1, and. 9.5 grams per liter respectively ofacetic, formic, lactic, and glycolic acids. In one run, black liquor wascooked directly without addition of sawdust. In the other runs, oaksawdust was mixed with the black liquor.

.7 The mixtures were heated in a three gallon gas fired autoclavewithout agitation. After cooking, the charge was allowed to cool, thereaction mixture was filtered and the Table 4 filtrate was analyzed forcontent of deslred aclds. In all Grams Grams Present After Cook runs thetime of heating was one hour and the temperature {gun 3 2:1 1 314101:Tgrp,

o s 1 o. oo iquor was 260 C. The data are summarised 1n Table 3 below.Solids, Acetic Forms Lactic elycofic Table 3 50 100 200 4. 2 8.0 6. 4 4.s 50 160 250 5.1 7.1 8.7 7. 7 Run 1 2 3 4 5 50 100 295 6.5 5.9 9.0 5.2

Grams Oak Sawdust 0 100 400 400 400 Grams Black Liquor Solids 1, 200 1,200 1, 200 1, 600 800 Vol. of Liquid (liters) 3 3 4 3 l The black liquorsolids, before heatnig, contained 4.2 grams acetic, 5.2 Grams R id Obtin d 139 240 531 633 4 grams formic, 5.5 grams lactic, and 2.8 gramsglycohc acids. Acetic Acid:

Grams present aftcr cook 31.2 30.3 47.5 49.8 31.2 15 Grams before cook20.1 20.1 20.1 341: 17.4 EXAMPLE 5 grails fofrmcdggringicookn 5. 1 4. 221. 4 15. 0 13.8

ercent ormc aseouwo 4.2 5.4 3.8 F Percent diugrease (111m l; 1 10, 431 7A number of diflerent celluloslc materlals were heated ormic Aoi Gramspmsentamr cook 50.6 41 0 7M 5m with sodium hydroxide and sodlumcarbonate solution grams before 301; & separately under the cond1t1onsshown In Table 5 below. rrarns formed 11ringcool1.. 1.7 l.9 25.1 21.418.7 Y Percent{mmcdbasedonwoom V 62 M It will be observed that acetlc,f0rm1c, lact c, and gly- L rer en mcrease during cook... a 47 -3.9 51.332.5 57.4 cohc aclds form 1n all cases but that the relative amounts E3;g 5m 50'7 7L 4 73.2 4&9 varysomewhat, the most obvious differencebeing that a gramsFetoredcolok 33.2 113.2 34.23 22.1 relatively purecellulose g1ves lower ratios of glycolic to g i 21% $15 a? 25 lacticacids. The three different types of equipment degigg gg g duringcvvkm0-9 5247 15-1 -3 scribed more fully hereinbefore were used in thevarious ifi Mmrcook 3% 33,9 612 6&6 5 runs. Runs 1-5 were made in anelectrically heated one Grams before 2&5 3840 liter stainless steelautoclave with stirring. Run 12 was Grams formed during 0001s.... 5.110. 4 38.7 25. 6 24. 5 Pergcntformed basedonwooi 104 M 61 made in athree gallon, gas fired, steel autoclave wlthoutPercentmereasedurmgcook... 17.9 36.5 135.8 (57.4 128.9 Stirring Theother runs were made in ml. iron tubes immersed in water in a threegallon autoclave.

Table 5 R G C u 1 v 1 T 1 Yield:percent oicellulosic material un rams eu 0510 o imo emu, No. Material Grams Alkali ml. Hrs. C.

Acetic Formic Lactic Glycolic Oalrsawdust,50 25 Na1CO 350 2 260 4.5 7.20.9 9.1 -.do 9.3 Na011-.... 350 z 200 4.2 4.1 9.1 9.4 Pine sawdust, 50.-25 010100 350 2 200 3. 2 4. 6 9. a s. 2 Pine Bark, 50. 25 'NazCOa 350 2200 2. s 4. 2 6.8 4. 0 Pine Chips, 400.. 150 NaOH. 3000 1 250 3.0 s. 910.6 0. 0 Sericea, 50.... 20 NaOH. 300 1 200 4. 8 8.0 9. 5 7. 0 10 40NeoH. 300 1 200 5.3 7.0 11.0 7.0 Cellulose, 5 20 NaOH. 300 1 250 2.111.7 13.5 0.5 .....de... 25 NaOH 125 1 260 2.0 10.2 12.0 6.2 --...do....25 Na2003 300 1 260 1. 4 8.2 4.7 3. 3 Cellulose, 2000112003.... 3000 1260 1.7 10.8 8.4 0.0 Cellulose, 50Na4OO 300 1 260 1.0 9.4 3.2 6.0

EXAMPLE 4 A series of runs was made which show the effect of temperatureon the amount of acetic, formic, lactic, and glycolic acids that formwhen oak sawdust is heated with black liquor from the sulfate pulpingprocess. centrated black liquor containing 49.5% solids was used afterbeing diluted with water to a volume of 500 ml. The ratio of sawdust toblack liquor solids was 50 grams to 160 grams. The grams of organicacids originally present in the black liquor were: 4.2 acetic, 6.2formic, 5.5 lactic, and 2.8 glycolic. The mixture of black liquor andsawdust was cooked in an electrically heated one liter bomb. Thetemperature was held at the indicated maximum temperature for two hoursbut the total time of heating varied depending on the time for heatingand cooling the charge. The total time of heating was greater in thecase of the higher temperature cooks. The data show that under theseconditions the best yields of lactic and glycolic acids occur in therange of 250 ".295 C. At higher temperatures, the yield of acetic acidincreases but the other acids are partially destroyed with the resultthat after cooking at 320 C. for two hours the solution contains lessformic, lactic and glycolic acids than were present in the black liquorat the start of the cook.

Con-

EXAMPLE 6 As described hereinbefore, in the production of acetic,formic, lactic, and glycolic acids by heating sawdust with aqueoussolutions of alkali, it is possible to build up the concentration ofacids by using the liquor from one cook in place of water forpreparation of the alkaline solution. In a series 'of such cooks, thecharge for the first cook was prepared by dissolving grams of sodiumcarbonate in 3000 ml. of water. The resulting solution was mixed with400 grams of sawdust and the mixture was heated for one hour at 260 C.in a three gallon steel autoclave without stirring. After heating, themixture was filtered and the residue washed with a little water. Thecombined volume of filtrate and washings was slightly larger than theinitial volume of alkaline solution. A portion of this solution wasanalyzed for its acid content and 3000 ml. of the solution, afteraddition of 160 grams of Na2CO3, was used for cooking another 400 gramportion of sawdust. As shown in Table 6 below, the concentration of saidacids in the cooking liquor can be increased substantially in thismanner. Contrary to expectation, viscosity of the solution does notincrease appreciably, indicating that whatever derivatives of the woodremain in: solution: must be of: relatively smallmolecular weight.

The data in- Table 6 give both the amounts of the acids formed duringeach cook and the. total amount in 10 Afterthecharge had: cooledit was.removed fromtheautdcla-ve and filtered. Aportion of the'filtrate wasanalyzed todetermine the amounts or" each. of the acids that werepresent as sodium salts. The data obtained are given in Table 8: below.

the filtrateafter each cook.

Table6 Amount of Acids in Grams Times .Grams .MLFil- Run No. RecookedResidue tram Acetic FOIHIIC Lactic Glycollo 1. Formed in cook. 2; Totalinfiltrate.

Table8 EXAMPLE 7 Yield of Acids in Grams g RunNo Grams Grams ThlSexample shows the efiect of temperatures on the Wood Nmoot- AceticFormlc Lactic Glycolic yield=ofi organic acids. In each run, 1600 gramsof oak sawdust was-suspendedin" 12,000 ml. of anaqueous solu- 533 6614 95 tioncontaining 800 grams of sodium carbonate and heatggg I 32- 32::2%; ed for one-hour at the indicated temperature 1n a S-gal- 1011electrically heated autoclave with. agitation. After the indicatedperiod of heating, the material was: cooled to about C.- C., thecontents of the autoclave was filtered, and a portion of the filtratewas analyzed to determine the amounts of acetic, formic, lactic, andglycoli'c acids which are present in the solution in the In order toshowmorespecifically the relationship between the amount of alkaliandyield ofproduct, the data in Table 8- were used to calculate the acidyields based on. both wood and amount of NazCOa as shown in Table 8-A.This latter data are reported as grams of acid obtainedxper. 100. gramsof wood used, and grams of acid obtained per 100 grams of NazCOa;

Table 8-41 Acetic Formic Lactic Glyeolic Total R N 17 7 an o. oo

Na 00 1 10 0 100 g./100 g. g./100g. g;/100 g. g. 100 g. gl/lOU g. g. 100g./100 g; g./I0O g.

2 8 V V00g 14 05, Wood Nazcoa WOOd. $26 03 WOOd 82053 WOOd NAECOI 4. 15'12. 46 7. 23 21. 5191 17. 5. 28 15; 22. 57 67. 76 4. 31 I In. 83 7. 19.88 6. 21 15. 53 5. 51 13. 78 23. 98 60. 02 4. 63 6. 95 1 9. 75 14. 65 7.75 11. 64 7'. 63* 11. 46 29. 76 44. 70

form of'their sodium salts. The data obtained in these tests are shownin Table 7.

This example shows generally the effect the amount of alkali has on acidyields. In each run, 1600 grams of oak sawdust was suspended in 12,000ml. of aqueous solution containing the indicated amount of NazCOa, andthe mixture was cooked for one hour at 270 C. in a S gaIIon electricallyheated autoclave with agitation.

As many apparently widely different embodiments of 5 this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereofi except as defined in the. appended claims.

What isclaimed is:

1.. Process of producing, saturated monocarboxylic acids, or saltsthereof, said acids having 1-3 carbon atoms in which one of the hydrogenatoms on the carbon atom adjacent the carboxyl group may be substitutedby an hydroxyl group, which comprises subjecting a mixture of cellulosicmaterial, alkali and water in the liquid phase, wherein Waterconstitutes a major part of the liquid phase, to a temperature of 250C.-300 C. in a closed system, and recovering. said salts from thereaction mixture.

2. Process of producing saturated monocarboxylic acids having l-3 carbonatoms in which one of the hydrogen atoms on the carbon atom adjacent thecarboxyl group may be substituted by an hydroxyl group, which comprisessubjecting a mixture of cellulosic material and an aqueous alkalinesolution to a temperature of 250 C.-300 C. in a closed system, the ratioof'water to alkali 3. Process of producing saturated monocarboxylicacids having l3 carbon atoms in which one of the hydrogen atoms on thecarbon atom adjacent the carboxyl group may be substituted by anhydroxyl group, which comprises subjecting a mixture of cellulosicmaterial and an aqueous alkaline solution to a temperature of 250 C.

9. Process of producing saturated monocarboxylic acids having 1-3 carbonatoms in which one of the hydrogen atoms on the carbon atom adjacent thecarboxyl group may be substituted by an hydroxyl group, which comprisessubjecting a mixture of cellulosic material and an aqueous solution ofan alkali selected from the group consisting of water. solublehydroxides and carbonates of alkali metal and alkaline earth metals to atemperature of 250 C.300 C. in a closed system, the ratio ranges 4.Process of producing saturated monocarboxylic acids having 13 carbonatoms in which one of the hydrogen atoms on the carbon atom adjacent thecarboxyl group may be substituted by an hydroxyl group, which comprisessubjecting a mixture of cellulosic material and an aqueous alkalinesolution to a temperature of 250 C.- 300 C. in a closed system,-theratio of water to alkali and the ratio of water to cellulosic materialbeing at least 3.5 to l and at least 4 to 1 respectively, removing anysubstantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution, and separating the acids from each other.

5. Process of producing saturated monocarboxylic acids having 1-3 carbonatoms in which one of the hydrogen atoms on the carbon atom adjacent thecarboxyl group may be substituted by an hydroxyl group, which comprisessubjecting a mixture of cellulosic material and an aqueous alkalinesolution to a temperature of 250 C.- 300 C. in a closed system, theratio of water to alkali and the ratio of water to cellulosic materialbeing at least 3.5 to l and at least 4 to 1 respectively, removing anysubstantial amount of insoluble material from the reaction mixture,purifying the reaction mixture by solvent treatment, acidifying thereaction mixture and thereby obtaining a mixture of said acids inaqueous solution.

6. Process of producing formic, acetic, lactic and glycolic acids, whichcomprises subjecting a mixture of cellulosic material and an aqueousalkaline solution to a temperature of 250 C. 300 C. in a closed system,the ratio ranges of water to alkali and of water to cellulosic materialbeing 3.5 to 37.5 and 4 to 30 respectively, acidifying the reactionmixture and thereby obtaining a mixture of said acids in aqueoussolution.

7. Process of producing saturated monocarboxylic acids having 1-3 carbonatoms in which one of the hydrogen atoms on the carbon atom adjacent thecarboxyl group may be substituted by an hydroxyl group, which comprisessubjecting a mixture of cellulosic material and an aqueous alkalinesolution to a temperature of 260 C.- 280 C. in a closed system, theratio ranges of water to alkali and of water to cellulosic materialbeing 3.5 to 37.5 and 4 to 30 respectively, removing any substantialamount of insoluble material from the reaction mixture, acidifying thereaction mixture and thereby obtaining a mixture of said acids inaqueous solution.

8. Process of producing saturated monocarboxylic acids, or saltsthereof, said acids having l-3 carbon atoms in which one of the hydrogenatoms on the carbon atom adjacent the carboxyl group may be substitutedby an hydroxyl group, which comprises subjecting a mixture of cellulosicmaterial and an aqueous solution of an alkali selected from the groupconsisting of Water soluble hydroxides and carbonates of alkali metalsand alkaline earth metals to a temperature of 250 C.300 C. in a closedsystem, the ratio ranges of water to alkali and of Water to cellulosicmaterial being 3.5 to 37.5 and 4 to 30 respectively, and recovering saidsalts from the reaction mixture.

of water to alkali and of water to cellulosic material being 10 to 25and 7 to 10 respectively, acidifying the reaction mixture and therebyobtaining a mixture of said acids in aqueous solution.

10. Process of producing saturated monocarboxylic acids having l-3carbon atoms in which one of the hydro-. gen atoms on the carbon atomadjacent the carboxyl group may be substituted by an hydroxyl group,which comprises subjecting a mixture of cellulosic material and anaqueous solution of an alkali selected from the group consisting ofwater soluble hydroxides and carbonates of alkali metals and alkalineearth metals to a temperature of 250 C.-300 C. in a closed system, theratio ranges of water to alkali and of water to cellulosic materialbeing 10 to 25 and 7 to 10 respectively, removing any substantial amountof insoluble material from the reaction mixture, acidifying the reactionmixture and thereby obtaing a mixture of said acids in aqueous solution.

11. Process of producing saturated monocarboxylic acids having l-3carbon atoms in which one of the hydrogen atoms on the carbon atomadjacent the carboxyl group may be substituted by an hydroxyl group,which comprises subjecting a mixture of cellulosic material and anaqueous solution of an alkali selected from the group consisting ofwater soluble hydroxides and carbonates of alkali metals and alkalineearth metals to a temperature of 260 C.280 C. in a closed system, theratio ranges of water to alkali and of Water to cellulosic materialbeing 10 to 25 and 7 to 10 respectively, removing any substantial amountof insoluble material from the reaction mixture, acidifying the reactionmixture and thereby obtaining a mixture of said acids in aqueoussolution.

12. Process of producing saturated monocarboxylic acids having 1-3carbon atoms in which one of the hydrogen atoms on the carbon atomadjacent the carboxyl group may be substituted by an hydroxyl group,which comprises subjecting a mixture of cellulosic material and anaqueous solution of sodium hydroxide to a temperature of 250 C.300 C. ina closed system, the ratio ranges of water to alkali and of water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

13. Process of producing saturated monocarboxylic acids having 1-3carbon atoms in which one of the hydrogen atoms on the carbon atomadjacent the carboxyl group may be substituted by an hydroxyl group,which comprises subjecting a mixture of cellulosic material and anaqueous solution of sodium carbonate to a temperature of 250 C.-300 C.in a closed system, the ratio ranges of Water to alkali and of water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

14. Process of producing saturated monocarboxylic acids having 1-3carbon atoms in which one of the hydrogen atoms on the carbon atomadjacent the carboxyl group may be substituted by an hydroxyl group,which comprises subjecting a mixture of cellulosic material and anaqueous solution of black liquor .to a temperature of 250 C. 300 C. in aclosed system, the ratio ranges of water to alkali and of Water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

15. Process of producing formic, acetic, lactic and glycolic acids,which comprises subjecting a mixture of cellulosic material and anaqueous solution of sodium hydroxide to a temperature of 260 C.-280 C.in a closed system, the ratio ranges of Water to alkali and of Water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

16. Process of producing formic, acetic, lactic and glycolic acids,which comprises subjecting a mixture of cellulosic material and anaqueous solution of sodium carbonate to a temperature of 260 C.280 C, ina closed system, the ratio ranges of water to alkali and of water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

17. Process of producing formic, acetic, lactic and glycolic acids,which comprises subjecting a mixture of cellulosic material and anaqueous solution of black liquor to a temperature of 260 C.280 C. in aclosed system, the ratio ranges of Water to alkali and of Water tocellulosic material being 10 to 25 and 7 to 10 respectively, removingany substantial amount of insoluble material from the reaction mixture,acidifying the reaction mixture and thereby obtaining a mixture of saidacids in aqueous solution.

References Cited in the file of this patent UNITED STATES PATENTS BraunDec. 17, 1935

2. PROCESS OF PRODUCING SATURATED MONOCARBOXYLIC ACIDS HAVING 1-3 CARBONATOMS IN WHICH ONE OF THE HYDROGEN ATOMS ON THE CARBON ATOM ADJACENT THECARBOXYL GROUP MAY BE SUBSTITUTED BY AN HYDROXYL GROUP, WHICH COMPRISESSUBJECTING A MIXTURE OF CELLULOSIC MATERIAL AND AN AQUEOUS ALKALINESOLUTION TO A TEMPERATURE OF 250* C.-300* C. IN A CLOSED SYSTEM, THERATIO OF WATER TO ALKALI AND THE RATIO OF WATER TO CELLULOSIC MATERIALBEING AT LEAST 3.5 TO 1 AND AT LEAST 4 TO 1 RESPECTIVELY, ACIDIFYING THEREACTION MIXTURE AND THEREBY OBTAINING A MIXTURE OF SAID ACIDS INAQUEOUS SOLUTION.